The middle phalanx in Poland syndrome.

The classic deformity of Poland syndrome consists of the combination of unilateral aplasia of the sternocostal head of the pectoralis major muscle and an ipsilateral hypoplastic hand with simple syndactyly and short fingers. The current study specifically investigates the abnormalities of the middle phalanx in a series of 15 patients with Poland syndrome. The degree of hand hypoplasia and finger brachydactyly was classified into 3 grades: mild (n = 2), moderate (n = 10), and severe (n = 3). The middle phalanges of all fingers in all patients showed abnormalities. The degree of deficiency in the middle phalanx (from mild hypoplasia to aplasia) correlated with the degree of brachydactyly, which in turn correlated with the degree of hand hypoplasia. Several other radiologic features of the hypoplastic middle phalanges were documented, such as the central nidus, the rounded or truncated appearance, and the cone-shaped epiphyses. The embryology of limb development was reviewed and it was proposed that abnormalities of the middle phalanx in Poland syndrome occur as a result of a mild ischemic insult during stage 19 of the embryonic life, leading to an arrest or lack of chondrification of the mesenchymal mass of the phalanx.